Ophthalmic test-lens set.



Patented May 7,1918.

2 SHEETS-SHEET l.

. A. H. KELLNER.

OPHTHALMIC TEST LENS SET.

APPLICATION FILED OCT. 9, 1916.

G.'A. H. KELLNER. OPHTHALNHC T EST LENSESET. APPLicATloN FILED ocT. 9. 191e.

Patented May 7,1918.

2 SHEETS-SHEET 2.

ATTORNEYS WTED STATES PA ENT FElE.

GUSTAV A. H. KELLNER, 0F ROCHESTER, NEW YORK, ASSIGNOR TO BAUSCH & LOMB OPTICAL COMPANY, OF ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK.

OPHTHALMIC TEST-LENS SET.

Specication of Letters Patent.

Patented May 7, 1918.

To @ZZ whom it may concern.'

Be it known that l, GUsTAv A. H. KELL- Nnn, a citizen of the United States, residing at Rochester, in the county of Monroe, State of New York, have invented certain new and useful Improvements lin Ophthalmic Test- Lens Sets; and I do declare the following to be a full, clear, and exact description of the same, reference being had to the accompanying drawings, forming a part of this specification, and to the characters of reference marked thereon.

My invention relates to optical instruments and more particularly relates to optometrical apparatus known as ophthalmic test or trial lens sets which comprise avariety of lenses each possessing d iiierent refractive qualities.

An object of the present invention isto provide a test lens set the individual lenses of which are so constructed and the ele ments of each of the lenses of which are so coordinated that the test set is simpler and more convenient in use and will yield more accurate and more `complete data for the making and litting of opthalmic lenses, than trial lens sets heretofore known. A further object is to provide a set of coordinated test lenses mounted in a novel manner, that is adapted to be manufactured accurately and economically and that is precise and convenient inuse.

ln the drawings: Figure l is a schematic diagram illustratingthe effect of lack of coordination of the elements of the diierent lenses forming an ordinary trial lens set; Figs. 2 and 3 are schematic diagrams illustrating a test lens set made in accordance with my invention; Fig. 4l is a schematic diagram on a smaller scale than the preceding figures, of a pair of test lenses made in accordance with my invention and held before the eye of a patient in a support embodying a gage for measuring the distance from the apex of the cornea of the eye to the adjacent vertex or principal point of the lens nearest the eye; Figs. 5 and o each illustrate on an enlarged scale, two lenses of a test lens set comprising a practical embodiment of my invention, arranged before the eye of ay patient.

Throughout the several igures or the drawings, the letter s either alone or with suitable sub-numerals has been used to denote spherical lenses, the letter c, either alone or with suitable sub-numerals, has been used to denote cylinder lenses, the letters P and P, in combination with the reference characters of the respective lenses as sub-numerals, denote the two principal points in each of the lenses, and the letters V and V, in combination with the reference characters of the respective lenses as sub-numerals, denote the two vertices of each of the lenses.

In ordinary ophthalmic trial lens sets the center thickness of the individual lenses of the set, that is, the distance from pole to pole of a lens along its optical axis, diiiers considerably in the various lenses of different powers in the set. Thus in the same se-t while the center thickness of each of the various negative lenses of di'erent powers will vary only a little, the center thickness of the plus lenses will vary a great deal, for example, a. plus 1 diopter spherical lens will probably have a center thickness of 1.8 nun., a. plus l0 diopter lens, a center thickness of 4.1 mm. and the center thickness of a plus 20 diopter lens will probably be 8.8 mm.

The result of this difference in center thickness in the various lenses of a `set is illustrated in Fig. l wherein I have represented an ordinary l diopter sphero trial lens s placed in position before the eye E, and in the same relative position thereto, I have shown in dotted lines, a lens s, having yapproximately the center thickness of an ordinary plus 2O diopter trial lens; but I have, in order to render the illustration more simple andv clear, provided the lens s, with a pair of curves that will give it the same power as the lens s whereby the equivalent focal length of the two lenses s and s, will be the same. I have also represented an ordinary a diopter cylinder trial lens arranged in position before the eye E in combination with either of the lenses s or s2. Through- 'out Figs. 1 to 4 of the drawings, the representations being purely schematic, I have for the sake of simplicity and clearness, diagrammatically shown the lenses as held in a support l0 by providing each of them with a peripheral groove arranged in a plane passing through the geometrical center of the lens at right angles to the axis thereof with which groove the inwardly projecting ribs l1 and 12 are adapted to cooperate, the A mail! el, .n

loriner with the sphero lenses and the latter with the cylinder lenses.

-ttvill he observed on reierringzz,L to Fig, l, that the principal point lys of the lens .s' lies farther troni the ape); A ot' the cornea than the principal point lys, otl the lens 3 presuininjg' that the axial distance ot the ribs 1l on the support l@ frein the apen il. et the cornea has not heen changed. This condition exists regardless ot the power ot the curves of the lens s2.

liecent investigation in the held ol3 ophthalinologv and optoinetrv has emphasized the importance ol properly locating the spectacle lens in liront ot' a patients eye and unless the diirterent locationsfof the principal points PS and lys, occurring; in actual use in the stronger and weaker lenses respectively', diie to their variation in center 'tliiclrness, he compensated tor, erroneous correction ot the patients elves will result, because the local point lieg of the thicker lens s, t'ails larther aivav troni the apen El. of 'the cornea than tl l'ocal point lle oi. the tliinner lensv rl`his er or in the actual correo tion vfill increase irregnlarlv with the power et the lens cinploved since the center thickness ot the lenses increases with their power and it the lenses he adjusted to provide a nnitorin corneal distance, that is, the distance l-Tv'ln, the error will he greater still because the dilerence hetvreen the position of the principal points lys and PS, with relation to the geometrical center G ot the respective lenses s and S, is not as great as the difference hetween the location ot the saine principal points lys and lys, with re lation to the adjacent vert-ee; TW@ or Vs2 ol their respective lenses S and S2, that is to say, that he distance G-la not as kgrreat as the distance VCS-Pk and Gwlws, is not as `great as "Weg-WST Difference in the center thickness ot the sphero trial lenses also affects the cylinder addition produced by a cylinder trial lens. 'llius when a cylinder trial. lens snch as c is placed in combination with a sphere trial lens heving a center thickness such as the lens s2, the cylinder power added as represented hv the distance hettvcen the astiginatic focal point llc, and toe local point is less than the c vlinder addition produced hv the saine cylinder trial lens c when it placed in coinhination 'with a sphere lens such as s, the lnder power added in the latter case lacing represented liv 'the distance between the astiginatic rpocal point Fc and the focal point ls. This difference in the cvlinder porter produced lov the saine cylinder trial lens when in combination at one time with a lens such as and at another 'til/ne With av lens such as s is due to the diierence in the distance 'troni the principal point 'F: to the principal point P82 when in. con'ihination With the S2 and,

dilerences in the center thicknesses of thev various cylinder trial lenses ol' a set ttvhich center thicknesses diler in the cylinder trial lenses sirnilarltY to the manne 1 in which they diter in the case oi"- the sphere trial lenses) adds still another complication "which is inet When the lenses ci an ordinary trial lens set are placed in combination. rl`his diiierence also manifests itself when the cylinder lenses are used alone before the eve E rbecause, With each dierent center thiclrness, the location ot the principal point Pc ivill var;7 relativelyT to the verten lf@ and with relation to the geometrical center Gc.

The above described variations in the relation of 'the principal. points in the varions lenses of a set ot ordinary trial lenses nialres it ver diticnlt to determine the location of 'the principal, points lys, lys,

and Pc either relativelj,7 to the apen il et the cornea or relativeljv to the tar point ot the eve i i test lens set may he inade in accordance with niv invention lov constructing 'the lenses of the set as illustrated in lligs. 2 and 3. ln snch a set et test lenses each oit the spherical lenses of the set., such as s, and si, will he inade of the saine torni, vrith the saine center thickness Vey-VS3, Thy-Va, and ot glass having' the same retractive index, and, in computing' the cnrves or refractive surfaces or" each ot the lenses, the constant center thickness is taken into co 'deration in order that the focal lengths, such as Pkg-W83, iger-FM or" all oi the lenses may enactl).7 agree with the nominal power ot the lens, Whether the lens he plus r ininus, of lovr power or ot high power. Likewise, the cylinder lenses snch as c2 el.' the setare all made oi: the saine torni, with the saine center thickness lcQ-Vc, and of haviini the saine retract-ive index, and in computing the curvature or refractive surface of each oli the lenses the constant center thickness ot the lenses is taken into ceration. Jn addition to this the refractive surface ot' each ot the cv der lenses :tor everv diterent power is so computed that any cvlinf lens o'll the set of any .civen power Will dnce eactlv the saine refractive e''ect on the eve as thonch cvlinder lens of that actual power were placed in the receptacle 'tor spherical lenses with its principal point P02 occupying; the position of the principal pointls oit the sphere lens. 'lhus presnniingl the lens o, to he marked as a l diopter cylinder lens the refractive etlect this lens *.vonld he identical with the reeliect ot a ldiopter cylinder lens ,need with its principal point Fc, co-

ioc

incident with the proper location of the principal point P293 of the sphero lens s3.

The result of this is that when an ophthalmic lens is made and the sphero curves and the cylinder curves are combined in one lens, and this lens is arranged at the proper distance in front of the patients eye; its eiiect on the eye will be identical with the elfect produced by the combination of the sphero and cylinder test lenses by means of which the eye was corrected when tested.

Another result is that when a cylinder correction alone is required and the correction is obtained by placing the cylinder test lens in its usual receptacle before the eye being examined, an ophthalmic lens made from the data thus obtained by the use of the cylinder test lens, will give exactly the same correction as was produced by the cylinder test lens.

Since all of the sphero lenses of the set are made of the same form, have the same center thickness and are made of the same glass, the distances Vsg-Psa, Ps3-Ps3, PsskVs in all of the sphero lenses through out the sphero lenses of the set will respectively, be the same. Thus, in the illustration given in Figs. 2 and 3, s3 represents a plus l diopter sphero lens, and s, a plus 20 diopter sphero lens, however, the distances VhS-Ps3, Psa-PSB, Ps3- VS3 are each respectively equal to the distances Vsf- 1?84, PSF-P84, RS4-V84. The sphero lenses of the set illustrated in Figs. 2, 3, and 4 are all shown to be double curved lenses and thus all of the sphero lenses of this set will either be double convex or double concave. The condition regarding the uniform location of each of the principal points in all of the lenses of the set with respect to their vertices will maintain, however, no matter what form of lens is used in constructing the sphero lenses of the test lens set, provided that they agree with the above requirements, namely, that all be alike in form, the same in center thickness and made of glass having the same refractive index.

Since all of the sphero lenses of the set are adapted to be located in the support 10 in the samel relation therewith, as is represented in the drawings by the ribs l1 cooperating with a centrally arranged peripheral groove in all of the lenses as hereinabove explained, it is clear that if the support l0 be adjusted to arrange one of the lenses of the set, say s3, with its vertex at a given distance from the apex A of the cornea of the eye, any other lens of the set such as sJr substituted in the support 10 in place of the lens s?i will occupy the same position and its various elements such as the vertex VSM the principal points 13's4c and Pal, will occupy the same position relatively tc the eye as the corresponding points of the preceding lens.

It has been stated that each of the cylinder lenses of a test lens set made in accordance with my invention is made of the same center thickness and of the same glass, and that all of the cylinder lenses of the set are adapted to be held in uniform relation to their support as represented by the coperation of the ribs l2 with the centrally arranged peripheral grooves in the lenses. The cylinder lenses are preferably made of the same form, each of them being plano convex or plano concave across the cylinder.

Thus in the case of the cylinder lenses also, the distances Vc2-Pc2, lyon2-V02J will throughout the cylinder lenses of the set, be respectively, the same.

Since the points V293, Pss, Ps3, and VS3 in each of the sphero lenses of the set will occupy the same position relatively to the elements ll when it is placed in the support adjacent principal points of the sphero and cylinder lenses when placed in combination will be the same with any combination of sphero and cylinder lenses in the set, and thus, when the cylinder lens c2 is placed in combination with the sphero lens s3 the cylinder power added as represented by the distance Fa- F03 is the same as when the same cylinder lens ca is placed in combination with another sphero lens s4, the cylinder power added in this case being represented by the distance Fei-Fcl.

With a test lens set made in accordance with my invention it is conveniently possible to measure the distance from the apex of the cornea of the eye under examination, not only to the adjacent vertex of the sphero lens or of the cylinder lens but also from the cornea to any of the principal points of the lenses. Since in practical use in my improved test lens set it is only necessary to know the location of the adjacent principal point of the lens such as Ps3 or PSL, of the sphero lenses placed immediately before the eye, because the cylinder lenses project, as it were, a hypothetical working principal point into the plane of the rearrnost principal points such as PSF.y or Ps of the spherical lenses: I will describe only the manner and means by which the distance from the apex of the cornea either to the adjacent vertex or to the adjacent principal point of the spherical lens placed before the eye under examination.

To this end, I provide on the support l0, a gage comprising a sight bar il() secured to one end of the scale bar 41 which is slidably mounted in the support at 42 and I provide a conveniens ineans sncli as 'bie lianclle il?) lei shillinglie scale longitudinally. FElie scale niej; eiliei le Qieisglecl Willi We sels ei? 'rannsiens one ellisse 'with i'elnlien te Jie einer eia clisn equal te tlie clisiance frein tlie see-i vetten ce ille ieainiese Qiincipal peinl; ns Wwf-Fiss, in alle lens s3, er

single scale may be nsecl liav'ing tive inclices sepninlecl by this saine Clisi-ence. ln Fig. Ll, l nwe slieifn 'the leiter ineiliecl7 llie edge #il ileiniing nn in cef'ipeieing with 'the scale when it is dev vcl te ienc lie clis- 1hence freni *elle apen l elI Jlie eei'nea le tlie ncljacens 'veilen liv/w53) ef alle splieiicel lens placed bei? .'e the eye, ancl *alle inclen en che .cle Off i-ne Winden' il@ is nsecl `Wlien i'e is clesiiecl lio niensuie 1lie 'j l ence 'ioin the apen ,L si ille cernes, el Me eye "ne ille ecljecent principal peint lys; of 'fille liest lens liele'e 'the effe el 'llie paiien't. iens el: lie seele nre se aiiengecl 'that lie inflex 1l-5 will cepeixete Willi 'lilie sie en llie seele when ille sighting peinis en 'ilie signi f as snewn in Fig, l nin alle i il'. leg, lilus being 'lie ien in Wliicli lie extieine L sight bnr is sliewn in cleicecl lines. El e indexing esige Us wil tlien eeenenie wiili lle n J 1 .L1 l.

zeie @ein when nie sighting points en ine sight bei il@ ie alinecl mili ille veilen W83 as shown in y el? che siglit bar being lien in the pesiiien in Wnicli il'- is slienn in full lines. llvlien le sigli .en i is niovel inte the pesitien will tlie. sighting peins in elinenienl; Willi ":lie einen :i ei the eeinea7 in Tliicli pesisici Jdie siliing bai' slieWi-i in cleltecl lines ii Jelle ef "elle lianfl eesieien7 in speci l i'li ielnbien te the in 'fe the ceinenl clis tance il ns )eel-ien 1the seele with felation te +lie inclen will give alie clisance frein Jdie einen i ef elle ccinen te ille piineipal peinnL PS3.

Essentially it is necessary in caiiying cui alie presens invention liethe eiiieal peins of all ei"- lie lenses ein' i sel7 'lli-nt is, elle principali peins, veiices and snppet engaging nieans and elf eenise Jdiese portions ci the snppei't which Willi the lenses te leegte tliein before lie eyes ci? a pacien@ lee se ceiclinaiecl vncl eclnpelile limi; when the lenses aie seleeliifely eiinn'ecl in nesitien before an eye el p and Clie sani-e piincipal eine ef each ei lie lenses inajf occupiT lelie seine pesiicn selalively le each eliel and ielacively 'te lelie eye. yllenfevei, ici praccical reasons it is giei'eielole 'il et hese pen'iions el the snppeit epeinling "ce lecaze ille lens lee, *ce es greas an extent is possible lined relatively "ce eseli etliei, :incl ielaliirely se ilie suppe' ii? and ii is pefeisble 'illes lie ceiclineien el 'line snnneii't u ienne, Elie veiices be efie niest uni-- is niacle nins lee the saine. UbViensly it is i not essential that the cennnen centei' thickef the spherical lenses lee equal te elle cennnen center iliiclniess el *alle cylinder enses, nei is it essentiel sluit lie sel: of plieicnl lenses and ille ses of cylinder lenses Y beli iii-ade of having ille saine ifeacliie incl-en, altlieugli usually lei: the salie .iiei'ni stenclaiclizaien it is peneiiecl ine the cenei1 thickness el Jalie splieicel cylinder lenses die sinne enel ite inalie all lenses el glass having the saine renfe inclen. i, nen cens'lineed iiei pi'actical use a test ,l inacle in scccinen-ce with my invenliien and lieietelice ennleinecl tlieei'eticsllj,T in connection Willi lliAv 2 enel 3 is piefeably censiinctec sliewn in Figs. 5 anal ell e"2 glie sphere lenses such S5 and 86 ancl the cylinder lenses sncli as 3 and c4 me insel@ eiliei @lane convex el? plane concave ci lie seine center lliicliness and el glass i the seine refiacliii'e index, ille constant een ite? thickness ef all of the sphere lenses being` islien inte censicleinieLA es in alle case el die AAses s3 and in computing their cinvatnie, enel lie cnivetnie ei the cylinclei1 lenses ccinpntecl 1relatively ce 'alle neininal @,sigiiaien el? eacli lens, that Wlien cylinder lens in position befcfe tlie eye, iis ies "inest principal peint sncli as Pca eii may be nesnniecl 'v'iitnally to lie in the the i'eai'inest piineipal peint such -s L a., er SG ei e splieie lens plncecl in pesnien befeie elle eye, as explained in connection Wiili JLilie cylinder lens c2 in Figs. 2 and 8.

lie lenses all being el' equal center 'tliicle ness enel 'the felation el the principal peints and. Alie veitices'being ille saine in all of lie le ases iielatiely te the pleno snifaee of Jlie lens7 it will be seen that the peiiplie'fy el lens enel its plane suffe-ce pievicle an excellentV ciiieiien lei' lecating 'the lens. Acceiclinglgf l 'provide the incnnling 52 having e peiiglicial fini adapted ce snugly fit in llie lens lielcleis er pockets l and Gil which ASi Lil@

cere of 1t-lie saine cliaine'er as the icecess consise Which the peripheral portion of the plano surface of the lens is adapted to be held.

l preferably make the bore 55 in all of the mountings of equal depth and compensate for the difference in edge thickness of the lenses, by providing spacing rings 57 of different Widths for relatively thin edged lenses as shown in Fig. 5 and, as shovvn in Fig. 6, by beveling off the relatively thick edged lenses in order to permit of spinning over the metal of the mounting to hold the lenses in place in the mounting.

lt will be observed that in the lenses of the set illustrated in Figs. 5 and 6, one vertex and one principal point in each lens is coincident. Thus in the sphero lenses S5 and sw the vertex such as Vs5 or VSG adjacent the eye E, and the adjacent or rearmost principal point, such as P295 or PSG are coincident; and therefore the back focus and equivalent focal length of any of the sphero test lenses, as placed before the eye of a patient, are the same; and also the distance from the apex A of the cornea to the adjacent vert-ex such as Vss or Vs6 of a lens, is the same as the distance from the apex of the cornea to the adjacent or rearmost principal point of said lens.

Accordingly, when the sight bar 60 of the corneal distance gage is arranged in line with the vertex of the sphero lens placed in the pocket 54 of the trial frame as shown in dotted lines in Figs. 5 and 6, the scale 8O to Which the sight bar is attached, coperating With any suitable index, such as the edge 82 of the scale bar guide 83 carried by the trial frame, Will register zero and When the sight bar is brought into alinement with the apex A of the cornea of the eye under examination, as shown in full lines in Figs. 5 and 6 the scale 80, cooperating With the index 82, Will register at once the distance from the apex of the cornea to the adjacent vertex and to the adjacent principal point of any sphero lens of the set placed in the trial frame pocket 53.

Having thus described my invention, What l claim and desire to secure by Letters Patent of the United States, is:

1. The combination with a support adapted to be adjusted before the eyes of a patient, of a plurality of lenses of different refractiveV qualities each having means for engagement with the support whereby said lenses may be interchangeably held in position to test the refraction of either or both of the patients eyes, the principal points, vertices and support engaging means of each of the lenses being so coordinated that When the lenses are selectively arranged in position before an eye of the patient, the same vertex and the same principal point of each of the lenses may occupy the same position relatively to each other and relatively to the eye.

2. The combination with a support adapted to be adjusted before the eyes of a patient, of a plurality of spherical lenses of different powers and a plurality of cylinder lenses of different powers, each of the lenses having means for engagement with the support whereby they may, singly or in combination, be held in position to test the refraction of either or both of the patients eyes, the principal points, vertices and support engaging means of each of the lenses being so c0- ordinated that the same vertex and principal point of any of the spherical lenses and the same vertex and principal point of any of the cylinder lenses Will occupy the same relative position While being used to test the refraction of an eye.

3. A plurality of test lenses of dierent dioptric powers adapted to be applied to a support and all having their principal points disposed in the same relation relatively to their geometrical centers, and support engaging means on each of the lenses arranged to hold those applied to the support in the same relative position.

4. The combination With a trial fra-me having one or more holders for supporting test lenses before an eye to be tested, of a plurality of test lenses having their principal points coordinated by making said lenses all of material of the same refractive index and with equal center thicknesses, and a plurality of mountings, one for each of the lenses, said mounting being so cordinated that the principal points and the vertices of the lenses held thereby will all occupy the same position relatively to the holder in which they are individually placed When testing the refractive properties of an eye.

5. ln an apparatus for testing eyes, the combination With a trial frame having a pair of alined test lens holders one for supporting sphero lenses and the other for supporting cylinder lenses before an eye to be tested, of a plurality of sphero test lenses of diil'erent dioptric povvers having their principal points and their holder engaging means disposed in the same relative positions, and a plurality of cylinder test lenses of different dioptric povvers each of said cylinder lenses when placed in its respective holder being adapted to provide a Working principal point in the plane common to the rearmost principal point of all of the spherical test lenses When placed in position in their respective holder.

6. In an apparatus for testing eyes, the combination With a lens support and a plu-v rality of lenses of diiierent refractive qualities adapted to be selectively placed before the eyes of a patient and having their principal points, their vertices and their support engaging portions coordinated, of a gage provided with means including a scale and index adapted simultaneously to indicate the distance from a given point to a gwn physical and izo en optical poiii' of e lens in lie suppoit.

7. The eon'iloinatioii Willi e liial frame having liolclei foiq suppotiiig tesi; lenses individually lieoi'e an eye lo loe testeil, of plurality of tesi lenses of clii'eifeii cliopiio 'powers encli having e plane opioel suiice and e curved opiezil surface zuid each pre- Viclefl Wim e iiel ,'zame engaging poi'tioii airaiigecl to liolcl J[lie Yeller; of irl/1e cuiiffe'cl suizice o eeeli of lie lenses in unifoi'm relation to the lens liolelei, said lenses eecli being adapted ze loe plaoefl with ilie iferei o: ils cuivecl siiifaee facing lle eye lo be tested, whereby che distance 'ioui lie cornea of ine eye being tesecl o Jlie Veitex of Jdie test leiis in rionl. lieieo'l miel the distance om szii. coiiiee to tlie aclieceiil; pfincipel point of said lens Will Toe the same and Wlieielijf the lens is adapted to denote ille reimetioiial ooiiecticii in terms of the beck focus of 'the lens.

8. The Coiiibinetoii with af trial frame having a lest lens liolclei, a pluraliy of l plano convex and plano concave test lenses of lie same center thickness-enel each llaving ilieir miiicipal points and their verices in ille same position relatively o the plane surface of the lens, of plurality of mountings one for each o the lenses, said mounings each lowing e portion adapted to entlie lens helder and a lens seat claptecl o engage Willi the ple-no suifece of the lens lielcl tlieiein at its periphery, the lens liolilei engaging poitions of all of elle meantings being oisposefl in the same relative posinon.

*GUSTAV A. KELLNER. 

